The present invention relates to detecting the presence of pathogens trapped in an electric field of a fluidic device, particularly to pathogens attached to antibodies immobilized in the electric field, and more particularly to the use of impedance measurements for detecting the presence of pathogens attached to antibodyxe2x80x94coated beads located in the electric field.
Dielectrophoresis (DEP) is currently utilized to collect or concentrate pathogens in an electric field of a fluidic device. Recently, interdigitated electrodes have been patterned on the surface of a fluidic channel for generation of a non-uniform electric field by applying a voltage across the electrodes and pathogens are trapped by the dielectrophoretic force.
One typical method of detecting pathogens is to detect whether or not they attach to specific antibodies. The antibodies are typically fluorescently labeled and this increase in fluorescence is detected optically. Multiple pathogen detection has been accomplished by immobilizing antibodies on a surface, and then introducing pathogens in a fluid to the surface. The pathogen binds to the surface and then are detected by optical means.
Recently, impedance measurements across adjacent electrodes has been utilized to detect the presence of trapped pathogens, and such an approach has been described and claimed in co-pending application Ser. No. 09/738,927, filed Dec. 13, 2000, entitled xe2x80x9cUsing Impedance Measurements For Detecting Pathogens Trapped In An Electric Fieldxe2x80x9d, assigned to the same assignee.
The present invention expands the impedance measurement approach to detect the presence of pathogens attached to immobilized antibodies, and to the use of antibody-coated beads for enhancing the impedance change to amplify this impedance change signal. The present invention utilizes patterned interdigitated electrodes located on the surface of a fluidic channel with an AC or DC voltage is applied across the electrodes, antibodies are immobilized on the surface of the electrodes and pathogens flowing in a sample fluid therepast are attached to the immobilized antibodies causing a change in impedance between adjacent electrodes. This impedance change can be enhanced by providing antibody-coated beads that attach to the pathogens thereby causing a greater impedance change.
It is an object of the invention to detect pathogens attached antibodies in a fluidic flow channel.
A further object of the invention is to detect the attachment of pathogens to immobilized antibodies in an electric field by measuring impedance change between adjacent electrodes caused by the presence of the pathogens.
Another object of the invention is to detect the attachment of antibodies to pathogens using the change of impedance between two electrodes.
Another object of the invention is to provide a sensor to detect the presence of pathogens trapped in an electric field or attached to antibodies immobilized in the field by measurement of impedance changes between two patterned electrodes located in a fluidic channel.
Another object of the invention is to enhance an impedance change signal causes by pathogens being trapped in an electric field by providing antibody-coated beads that attach to the trapped pathogens causing a greater impedance change.
Another object of the invention is to detect pathogens trapped in an electric field by providing antibody coated beads which attach to the pathogens causing further change in the impedance between two electrodes, and moving the thus coated beads in an out of the signal region.
Another object of the invention is to provide a device for measuring impedance change in electrodes located in a fluidic channel and caused by trapped pathogens, and providing a second set of electrodes to act as a reference signal.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. The present invention is directed to the use of impedance measurements to detect the presence of pathogen attached to antibodies, and more particular to pathogens attached to antibody coated beads. Basically, the present invention replaces the prior optical detection approach with the detection of the attachment of antibodies to pathogens using the change of impedance between two electrodes as a way of making a less expensive pathogen detection system. The detection system or sensor of this invention, may for example, use patterned intedigitated electrodes on the surface of a fluid channel, with an AC or DC voltage applied across the electrodes to produce a non-uniform electric field. Antibodies are immobilized on the surfaces of the electrodes and the impedance between the electrodes is measured. Following the passage of a sample fluid containing pathogens through the fluid channel and by the electrode surface, certain of the pathogen are attached to the immobilized antibodies, thereby causing a change in the impedance between the electrodes, which change of impedance provides a measurement by which the presence of the pathogens can be determined. To amplify the impedance change signal, antibody coated bead may be introduced which attach to the trapped pathogens causing a greater change in impedance between the electrodes. The pathogen sensor of this invention can be used, for example, in counter biological warfare detectors to detect the presence of pathogens, or in any antibody-based assay system.